Method of contacting feed oil with coke in the fluid contact coking of residual oils



METHOD OF CONTACTING FEED OIL WITH COKE IN THE FLUID CONTACT COKING OF RESIDUAL OILS Filed April 12, 1955 July 14, 1959 I c. 1.. CRAWLEY 2,894,899

C'oke' HOPPEQ 1 u FEED 0/4- E FZwo caA/wcr /2 52212556 Calm z: Panama United States Patent METHOD OF CONTACTING FEED OIL WITH COKE ltNALTkggll-s FLUID CONTACT COKING OF RESID- Carroll L. Crawley, Port Arthur, Tex., assignor to Texaco Inc., a corporation of Delaware Application April 12, 1955, Serial No. 500,845 2 Claims. Cl. 208-127) This invention relates to the cracking and coking of heavy hydrocarbon oils in contact with highly heated powdered or pulverulent coke under fluidized conditions and is concerned particularly with the method of contacting the feed oil with highly heated coke for delivery to the fluid contact coking zone.

The advantage of the fluid contact coking process is concerned particularly with the processing of heavy residual stocks. However, difficulty has been encountered in obtaining proper contact between the residual oil and the coke particles. It has been found that when introducing the heavy oil into contact with a fluidized mass of coke particles there isa considerable tendency toward the fonnationo'f agglomerates of heavy oil constituents and'coke-particles: The resultant agglomerates interfere with the fluidization. The invention presents a method of overcoming these difliculties.

In accordance with the invention the feed oil is introduced into contact with highly heated coke particles descending in a substantially free falling column of discrete particles. The oil is dispersed over the downfalling particles and the heat in the particles causes vaporization and deposition of residue on the particles. The coke particles coated with residue descend without obstruction by any up-flowing gas. The vapors and gases produced flow in the same direction as that of the falling coke particles. Coated coke particles together with the vapors and gases generated pass freely into an enlarged chamber wherein fluid contact coking conditions are maintained and the coking operation is completed.

The process is adapted particularly for the cracking and coking of residual stocks, such as reduced crude petroleum, cracked residues, heavy residues from shale oil, tars from the carbonization of coal and other heavy residues, to produce gasoline as well as gas oil such as is adapted for subsequent catalytic cracking.

An important feature of this method of contacting the feed oil with the coke particles is that in the initial contacting the feed oil comes in contact only with the fresh coke which is passing to the fluidization zone and this coke of the initial contacting is at the maximum temperature to which the oil is subjected in the system.

In this method of contacting the heavy residual charge oil with the highly heated coke the individual coke particles are instantaneously wetted with the oil and freely descending in discrete particles are subjected to vaporizing and coking temperatures. Each particle of coke is separated from adjacent particles and is surrounded by vapors and gases while the particles are Wet and sticky. In a matter of seconds the descending particles drop through the dilute phase of the fluidization zone under hindered settling conditions where further drying occurs and finally are merged in the dense phase. Thus wet or sticky particles do not reach the dense phase and this source of agglomeration is eifectually prevented and the coking is completed under continued good fluidizing conditions.

2,894,899. Patented July 14, 1959 For the purpose of more fully describing the invention reference is had to the accompanying drawings wherein:

Figure 1 is a diagrammatic elevational view of an apparatus adapted for practicing the process of the invention.

Figure 2 is an enlarged view of a distributing device for controlling the feed of the coke into contact with the charging oil.

In the drawing 10 indicates a fluid contact coking chamber wherein fluid contact coking conditions are maintained with the formation of a dense phase at 11 and a superposed dilute phase or disengagement space at 12. Steam or hydrocarbon gas or other aerating medium is introduced by a line 13, and serves to maintain fluidization in the chamber. The evolved vapors and gases are removed through a cyclonic separator 14 which returns coke particles to the dense phase while the vapors and gases leave through a vapor line 15 to suitable fractionating and condensing apparatus (not shown) for recovering the products.

Coke particles from the dense phase descend through a standpipe or stripper 16 into which steam is admitted by a line 17 for removing any contained hydrocarbons from the coke and the stripped coke is picked up in a current of air or oxygen containing gas and the dispersion 10f coke and gas is directed through a pipe 18 in which combustion are separated from the coke particles. The

gases pass through a cyclonic separator 20 to flue gas line 21. The separated coke particles accumulate in a bed. Product coke is Withdrawn through a line 22.

Coke particles from the bed in separator 19 descend into a column 23 through a distributor 24. As shown in Fig. 2 the distributor is composed of plates 24a and 24b. Each plate is formed with a plurality of openings 25. The openings are arranged in a plurality of concentric rows and by rotating one of the plates the sizes of the respective openings through the pair of plates are regulated. The coke descends through the plate distributor to form a plurality of descending annular curtains of coke particles. The feed oil is admitted by a line 26 terminating in a down-turned nozzle for spraying the oil downwardly and across the several curtains of falling coke. A small amount of steam is preferably introduced with the feed oil to assist in atomizing and spraying the oil. Ordinarily the diameter of the column 23 will more or less approximate /a of the diameter of the fluidization chamber 10. Thus for example with a fluidization chamber of a diameter of 12 ft. the column 23 will have a diameter of about 3-4 ft. The oil spray is regulated so as to avoid spraying the oil on the wall of the column. The feed oil descending in the column 23, upon coming in contact with the highly heated coke, is subjected to flash vaporization and residual oil is deposited on the coke particles. The head of coke in the separator 19 prevents the passage of vapors and gases upwardly and the total efliuent descends through the column aided by the flow of gases and vapors and thence through the open end of the column into the fluidization chamber 10. Here the coke particles, as has been stated, are subjected to fluidization and the coking and cracking reactions continued.

In practicing the invention the feed oil is preferably heated to temperatures of the order of 700-800 F. for introduction into the column 23. The temperature in the column 23 runs about 1000-1100 F. A time of contacting therein of about 1-5 seconds produces coke particles of non-sticky character adapted for merging in the dense phase of the fluid. contact coking zone. The cracking and coking is continued under fluidized conditions in the chamber to the extent desired. The temperature in the fluidization chamber 10, without added heat, will ordinarily run somewhat lower than the column 23 such as about 50-10'0 F. lower. Operating in this manner the chamber 10 is essentially a soaking zone to effect further reaction. When higher temperatures are desired in the fluidization chamber 10 the fluidizing gas entering through line 13 is heated in order to raise the temperature of the fluidized mass. The process is conducted under pressures approximating atmospheric or at least under moderate superatmospheric pressures.

The air supplied the transfer line coke burner 18 is regulated so that the oxygen is completely consumed in the line and there is no continuance of burning in the separator 20.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a fluid coking process wherein a heavy residual oil is contacted with pulverulent coke particles and cracking and coking are effected in a fluidized bed of coke particles in a cracking and coking zone, cracked products are separated and withdrawn as a vapor from said cracking and coking zone, coke particles from said fluidized bed are separately withdrawn from said cracking and coking zone and subjected to combustion to form highly heated coke particles, the improvement which comprises forming a free falling column of said highly heated coke particles, initially contacting said oil with said highly heated coke particles by dispersing said oil over said highly heated coke particles in said free falling column forming oil-Wetted coke particles, maintaining said oilwetted coke particles at a temperature within the range of 1000 to 1100 F. in the form of a free falling column for a time within the range of about 1 to 5 seconds effecting conversion of said oil-wetted coke particles to vapor and non-agglomerating coke particles, and merging said non-agglomerating coke particles with said fluidized bed of coke particles.

2. An apparatus for cracking and coking a heavy residual oil in contact with pulverulent coke which comprises in combination an elevated hopper, a concentrically apertured distributor disposed at the bottom of said hopper, a vertical contacting column disposed below said hopper, said hopper debouching through said distributor into said contacting column, an oil inlet line terminating in an outlet discharging radially and downwardly axially of said distributor and within and near the top of said contacting column, a fluidization chamber disposed beneath said column, said contacting column debouching into said fluidization chamber, means for withdrawing vapor products from said fluidization chamber, means for the introduction of fiuidizing medium into said fluidization chamlber, means for withdrawing coke particles from a fluidized bed of coke particles maintained in said fluidization chamber, means for highly heating said coke particles, and means for transferring highly heated coke particles into said elevated hopper.

References Cited in the file of this patent UNITED STATES PATENTS 2,661,324 Lefier Dec. 1, 1953 

1. IN A FLUID COKING PROCESS WHEREIN A HEAVY RESIDUAL OIL IS CONTACTED WITH PULVERULENT COKE PARTICLES AND CRACKING AND COKING ARE EFFECTED IN A FLUIDIZED BED OF COKE PARTICLES IN A CRACKING AND ZONE, CRACKED PRODUCTS ARE SEPARATED AND WITHDRAWN AS A VAPOR FROM SAID CRACKING AND COKING ZONE AND SUBJECTED TO COMBUSTION TO FORM IZED BED ARE SEPARATELY WITHDRAWN FRROM SAID CRACKING AND COKING ZONE AND SUBJECTED TO COMBUSION TO FORM HIGHLY HEATED COKE PARTICLES, THE IMPROVEMENT WHICH COMPRISES FORMING A FREE FALLING COLUMN OF SAID HIGHLY HEATED COKE PARTICLES, INITIALLY CONTACTING SAID OIL WITH SAID HIGHLY HEATED COKE PARTICLES BY DISPERSING SAID OIL OVER SAID HIGHLY HEATED COKE PARTICLES IN SAID FREE FALLING COLUMN FORMING OIL-WETTED COKE PARTICLES, MAINTAINING SAID OILWETTED COKE PARTICLES AT A TEMPERATURE WITHIN THE RANGE IF 1000 TO 1100*F. IN THE FORM OF A FREE FALLING COLUMN FOR A TIME WITHIN THE RANGE OF ABOPUT 1 TO 5 SECONDS EFFECTING CONVERSION OF SAID OIL-WETTED COKE PARTICLES TO VAPOR AND NON-AGGLOMERATING COKE PARTICLES, AND MERGING SAID NON-AGGLOMERATING COKE PARTICLES WITH SAID FLUIDIZED BED OF COKE PARTICLES. 